U.S. Pat. No. 4,162,993 describes a catalyst support formed by winding a single strip of metal upon itself, wherein the spacing between layers of the spiral is uniform and equal to the height of the indentations in the strip. The indentations are spaced along the strip in a pattern that varies, and is not repeated in any layer of the spiral. By varying the pattern in this way, the indentations in successive layers are prevented from nesting together. If the indentations are formed by passing the strip between a pair of die wheels, and if the circumference of the die wheels is at least as great as the diameter of the finished spiral, and if the pattern of spacing is not repeated around the circumference of the die wheels, then the indentations in successive layers cannot nest together. This is the essence of U.S. Pat. No. 4,162,993. It is an economical way to construct spirals of small diameter, say for automobile mufflers and for small catalytic combustors. But for spirals having a diameter of more than about 20 cm., the cost of the die wheel is excessive. An object of the present invention is to enable us to wind spirals of any diameter, using die wheels having a diameter that is both smaller than, and independent of, the diameter of the spiral.